NMEA 2000

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NMEA 2000 is a combined electrical and data specification for a marine data network for communication between marine electronic devices such as depth finders, nautical chart plotters, navigation instruments, engines, tank level sensors, and GPS receivers. It has been defined by, and is controlled by, the US based National Marine Electronics Association (NMEA).

NMEA 2000 connects devices using Controller Area Network (CAN) technology originally developed for the auto industry. NMEA 2000 is based on the SAE J1939 high-level protocol, but defines its own messages. NMEA 2000 devices and J1939 devices can be made to co-exist on the same physical network.

NMEA 2000 (IEC 61162-3) can be considered a successor to the NMEA 0183 (IEC 61162-1) serial data bus standard. It has a significantly higher data rate (250k bits/second vs. 4800 bits/second for NMEA 0183). It uses a compact binary message format as opposed to the ASCII serial communications protocol used by NMEA 0183. Another improvement is that NMEA 2000 supports a disciplined multiple-talker, multiple-listener data network whereas NMEA 0183 requires a single-talker, multiple-listener (simplex) serial communications protocol.

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[edit] Network Construction

The NMEA 2000 network, like the SAE J1939 network on which it is based, is organized around a bus topology, and requires a single 120Ω termination resistor at each end of the bus. The maximum distance for any device from the bus is six metres.

Typical NMEA 2000 Network Installation
Typical NMEA 2000 Network Installation

[edit] Cabling and Interconnect

The only cabling standard approved by the NMEA for use with NMEA 2000 networks is the DeviceNet cabling standard, which is controlled by the Open DeviceNet Vendors Association. Such cabling systems are permitted to be labeled "NMEA 2000 Approved". The DeviceNet standard defines levels of shielding, conductor size, weather resistance, and flexibility which are not necessarily met by other cabling solutions marketed as "NMEA 2000" compatible.

There are two sizes of cabling defined by the DeviceNet/NMEA 2000 standard. The larger of the two sizes is unfortunately denoted as "Mini" (or alternatively, "Thick") cable, and is rated to carry up to 8 Amperes of power supply current. The smaller of the two sizes is denoted as "Micro" (or alternatively, "Thin") cable, and is rated to carry up to 4 Amperes of power supply current.

Mini cable is primarily used as a "backbone" (or "trunk") for networks of larger vessels (typically with lengths of 20 m and above), with Micro cable used for connections between the network backbone and the individual components. Networks on smaller vessels often are constructed entirely of Micro cable and connectors.

[edit] Device Certification

Devices go through a rigorous certification process overseen by the NMEA, and are permitted to display the "NMEA 2000 Certified" logo once they have completed the certification process. The certification process does not guarantee data content, that is the responsibility of the manufacturers. However, the certification process does assure that products from different manufacturers assemble and exchange data in a compatible way and that they can coexist on a network.

[edit] NMEA 2000 and SmartCraft

The SmartCraft standard was developed by Brunswick Corporation, and is used by Mercury Marine and some Cummins engines (many Cummins engines also support the J1939 data protocol). While SmartCraft uses the same CAN technology as NMEA 2000 for its electrical signaling and low level protocol, the two networks uses different high level data protocols; therefore, devices designed for one network cannot operate on the other.

[edit] Trademarks

The term "NMEA 2000" is a registered trademark of the National Marine Electronics Association. Devices which are not "NMEA 2000 Certified" may not legally use the NMEA 2000 trademark in their advertising.

[edit] Manufacturers

The following companies manufacture NMEA 2000 certified products:

  • Airmar
  • Beede Instruments
  • Blue Water Data
  • CPAC Systems AB
  • Digital Switching Systems
  • Evinrude/BRP
  • FW Murphy
  • Faria Instruments
  • Furuno
  • Garmin
  • Jeppesen Marine (formerly Nobeltec)
  • Kvaser
  • Lowrance
  • Maretron
  • Molex
  • Offshore Systems (UK) Ltd.
  • Raymarine
  • Simrad
  • Teleflex
  • Yamaha Marine
  • Westerbeke Corp.
  • Xantrex Technology, Inc.
  • ZF Marine Electronics

[edit] External links